Amputees can secure prosthetic devices on their residual limbs by using various vacuum or suction arrangements, whereby the maximum strength of the force holding the prosthesis to the residual limb is a function of the atmospheric pressure. The differential air pressure is routinely referred to as suction or vacuum by those having skill in the art. To maintain the sub-atmospheric pressure created within the distal end of the socket, sealing sleeves or liners have been provided to prevent an influx of air around the distal end of the residual limb. Such liners are provided between the residual limb and the socket to provide for slight compression, and a gripping connection is provided to assist with the suction suspension.
The liner can be rolled onto the residual limb so the liner-covered limb can then be inserted into the prosthetic socket. Using conventional liners alone only provides a partial suction fit since they form no true air-tight seal with the socket. Some air will slowly enter the socket, especially during the swing phase of the patient's gait and during periods of inactivity.
Using a valve should allow air to be expelled from the socket in order to maintain at least a slight negative pressure for creating the suction against the residual limb. Although the swing phase of the gait cycle will pull the socket off the limb, walking and other weight-bearing activities may push the limb further into the socket. Pushing the limb further into the socket causes the valve to expel air. Conversely, directly pulling the limb out of the socket is prohibited due to the effect of suction. Using a valve is also helpful in preventing a positive pressure within the socket interior relative to the ambient air outside the socket to allow donning the prosthesis on a limb. Common valve systems used with sockets have included a valve member mounted in a cavity that moves between a sealed position and a vented position and a biasing member biasing the valve member to its seated position.
Unfortunately, conventional valve systems such as these suffer from several drawbacks. For instance, such systems often delay a tight and secure fit as a prosthetic user dons the socket because of poor air flow and air resistance. The poor air flow and air resistance of such valve systems also can decrease the suction applied to the residual limb, which may cause it to become disengaged during use. Many existing valve systems include components protruding from the socket, making it cumbersome and uncomfortable to wear, while also increasing the chance it may snag onto foreign objects. By not keeping a low profile, there is also a greater likelihood of the valve system being damaged. The sealing strength of such valve systems can also be insufficient or limited. Damaging the valve or compromising the seal strength would cause the air pressure within the socket to no longer be properly maintained, and the suspension it provides to the residual limb would ultimately fail.
In view of the shortcomings of conventional valve systems, there exists a substantial need for a valve that improves suspension and makes it easier to don and doff a socket.